html, body {
  margin: 0; padding: 0;
  height: 100%;
}

.rect {
  width: 100%; height: 100%;
}

.white {
  @extend .rect;
  background-color: white;
},

.red {
  @extend .rect;
  background-color: red;
},

.blue {
  @extend .rect;
  background-color: blue;
}